JP6184710B2 - Material for use in a magnetic resonance system, method for producing the material, and magnetic resonance system - Google Patents

Description

  The present invention relates to a material for use in a magnetic resonance facility, a method for manufacturing the material, and a magnetic resonance facility including components made of the material. In particular, the present invention relates to materials with reduced visibility in magnetic resonance imaging.

  Magnetic resonance (MR) imaging is an imaging method used for examination and diagnosis in many areas of medicine. The physical effects of nuclear spin resonance form the basis. In order to extract the MR signal, a basic magnetic field is applied in the examination region using a basic magnetic field magnet, which aligns the magnetic moment of the nucleus, for example the hydrogen nucleus H-1 or the nitrogen nucleus N-14.

  By irradiation with radio frequency (hereinafter referred to as HF) pulses, the nuclear spins can be diverted or excited from an aligned position in parallel to the basic magnetic field, i.e. in a static position, or in other states. During the period of relaxation to the static position, a decay signal occurs, which can be inductively detected as an MR signal using one or more HF received pulses. For example, proper dephasing and rephasing of nuclear spins can obtain MR signals with appropriately switched gradient fields. Such an effect is used in a so-called gradient echo MR imaging sequence.

  By attaching a slice selection gradient during irradiation with a high-frequency pulse, only the nuclear spin in one slice to be examined is excited, and the resonance condition based on the local magnetic field strength is satisfied in the slice. Other spatial encodings can be performed by appending at least one phase encoding gradient and a frequency encoding gradient during the reading period. Thereby, MR signals can be obtained spatially resolved from a plurality of slices of the subject. By using an appropriate display method, it is possible to use a three-dimensional (hereinafter referred to as 3d) image of a specific area of the subject for diagnosis. At that time, the typical spatial resolution of MR image formation can take a value of, for example, 1 mm in all three spatial directions. Such locally spread image forming points are called voxels.

  For MR imaging, at least the patient on the bed or table is brought into the basic field magnet. In addition, an HF local coil is used to improve MR imaging and this coil is located in the immediate vicinity of the patient. Thereby, not only the patient but also other parts made of various materials, such as a bed or a coil, are present in the imaging space. However, because these materials contain nuclei that are also used for MR imaging, they may be imaged as well.

  The imaging properties of the material present in the examination area used for MR imaging can cause artifacts in the MR image. Such artifacts can lead to inaccurate diagnosis or make the image diagnostically unusable. In empirical tests, only relatively few materials are known that have reduced visibility in MR imaging. Along with the reduced visibility in MR imaging, other criteria for availability within the MR facility are still critical, such as zero or low conductivity and zero or low susceptibility. So the number of materials that can be used is limited.

  This results in increased costs in the manufacture of components for use in MR equipment, for example, since synthetic materials that are obviously less expensive cannot be used. Further, for example, soft and flexible synthetic materials are known from various areas of daily life, but they do not have reduced visibility in MR imaging and can therefore be used as bulk materials. Can not. This results in reduced comfort and limited design freedom when using or manufacturing components for use in MR equipment. Furthermore, it may not be possible to use materials that are particularly well processable or that are particularly tough or stable. This can result in reduced reliability of components for use in MR equipment or reduced lifetime.

  For example, a technique is known in which the magnetic susceptibility of a base material can be matched with a predetermined fixed value by mixing at least one of a paramagnetic substance and a diamagnetic substance (for example, Patent Documents). 1). However, the technique disclosed therein relates to a reduction in magnetic susceptibility mismatch so that the static magnetic field varies on a length scale of several centimeters and deviates from the desired value of the basic magnetic field. Thereby, for example, misalignment or position space distortion in the MR image may occur, or the quality of the spectral fat saturation technique may be negatively affected. However, the material visibility in MR imaging is not controlled.

US Pat. No. 7,604,875 B2

  Therefore, there is a need to provide a technique that can be used for components of MR equipment and that can provide a material that does not have the disadvantages described above and has reduced MR visualization. There is a need to provide a technique for supplying various substrate materials with reduced visibility in particular.

This object is achieved according to the invention in that a material for use in a magnetic resonance facility comprises a base material and a magnetic doping material mixed in a defined proportion, and within a volume of less than 1 mm ^{3 of} said material. This is solved by a material for use in a magnetic resonance facility in which a substantially uniform mixing of the substrate material and the doping material is present (claim 1).
Advantageous embodiments of the present invention relating to materials for use in magnetic resonance equipment are as follows.
The particle size of the doping material is less than about 200 μm, preferably less than about 10 μm (claim 2);
The doping material comprises magnetic nanoparticles and the particle size of the doping material is less than about 1 μm, preferably less than 100 nm (claim 3);
The magnetic nanoparticles are ferromagnetic (Claim 4).
The proportion of the doping material is in the range of 0.1% to 80%, preferably in the range of 1% to 20%, particularly preferably in the range of 9 to 11% (Claim 5).
The substrate material is an acrylonitrile-butadiene-styrol (ABS) synthetic material (claim 6).
The substrate material is selected from the following group of thermoplastic substances, thermoplastic elastomers, elastomers, thermosetting substances, and foamed plastics (Claim 7).
The doping material is selected from a first group of diamagnetic materials including graphite, bismuth as components, or a second group of paramagnetic materials including platinum, chromium, tungsten, ferritin as components (Claim 8).
The material has a macroscopic susceptibility approximately equal to that of water or tissue or organic material or air (claim 9);
The material has a macroscopic magnetic susceptibility not equal to at least one magnetic susceptibility of water and tissue and organic material and air (claim 10);
The material has a T2 ^* relaxation time of nuclear spin in the volume, the relaxation time being 1/2 times, preferably 1/4 times smaller than the corresponding T2 ^* relaxation time of the substrate material (claim 11) ).
The material comprises another magnetic doping material mixed in another proportion, and there is a uniform blend of the substrate material and the doping material and the other doping material in the volume; The sign of the magnetic susceptibility of the doping material is not equal to the sign of the magnetic susceptibility of the doping material.
The particle size of said further doping material is smaller than 100 μm, preferably smaller than 10 μm (claim 13).
-The proportion of the doping material and the proportion of the other doping material are different, and the macroscopic susceptibility is equal to a defined value (claim 14).

In order to produce a material for use in a magnetic resonance facility according to the present invention,
A base material made of a synthetic material is melted by an extruder,
Solved by a method of manufacturing a material for use in a magnetic resonance facility that mixes the proportion of magnetic doping material so that there is a uniform mixing of the base material and the doping material in a volume of less than 1 mm ³ (claims) Item 15).
Embodiments of the present invention relating to a method for producing a material for use in a magnetic resonance facility are as follows.
-It is used to produce the material according to the invention (claim 16).
Further, according to the present invention, the magnetic resonance equipment having a sensitivity region is configured to detect magnetic resonance data for image formation in the sensitivity region, and the magnetic resonance equipment Therefore, a component is included in the sensitivity region, which component is also solved by a magnetic resonance installation comprising a material according to the invention (claim 17).

According to one aspect, a material for use in a magnetic resonance (MR) facility is provided. The material includes a base material and a magnetic doping material added at a defined ratio, and there is a substantially uniform mixing of the base material and the doping material within a volume of less than 1 mm ^{3 of the} material.

  For example, the magnetic doping material may be diamagnetic, paramagnetic or ferromagnetic. The doping material can have a magnetic susceptibility different from that of the substrate material. For example, the substrate material may be non-magnetic, i.e. having no magnetic susceptibility or having very little magnetic susceptibility. However, the substrate material can also be magnetic.

Substantially uniform blending can mean, for example, that there is always a defined percentage of the doping material in a suitable (test) volume that is arbitrarily arranged and smaller than 1 mm ^3. . When mixing doping materials, non-uniformity and local or microscopic differences in concentration can occur. This is the case where there may be local regions or clusters in which the doping material is present at a concentration that is elevated relative to the average value, or where the substrate material is elevated relative to the average value. Is present at a given concentration. However, such inhomogeneities do not exist in observations averaged over volume, since mixing can be precise or uniform. In other words, the concentration gradient of the doping material may take a value different from 0 on a microscopic length scale or on a length scale less than 1 mm, while a specific gradient over a length of 1 mm or longer. Or the averaged concentration gradient is equal to or close to zero.

  When the material is brought into the basic magnetic field of the MR equipment due to the addition of the magnetic doping material having the magnetic susceptibility χ ≠ 0, the magnetic field locally deviates from the basic magnetic field strength within the material. This occurs, for example, due to the demagnetization effect of the magnetic doping material, which intensifies or weakens the external magnetic field. The corresponding physical phenomena of static magnetic fields are known to those skilled in the art and therefore need not be discussed in detail in this connection.

Therefore, microscopic inhomogeneity of the magnetic field occurs based on the locally changing magnetic susceptibility. In particular, the magnetic field on the representative length (also called “characteristic length” or “characteristic length”) related to the elaboration of the admixture and the (microscopic) geometry of the doping material varies. . That is, for example, it has a representative length smaller than 1 mm resulting from the size of the volume. Such uniform blending on a length scale of less than 1 mm results in reduced visibility of the material in MR imaging because spins are phasing faster, ie shorter T2 ^* relaxation times are achieved. Can result in having For example, the typical MR equipment's spatial resolution, or voxel size, may have an order of about 1 mm. This means that, for example, when MR signals are detected for a corresponding imaging volume of 1 mm ³ , they are averaged or integrated. As the magnetic susceptibility and thus the local magnetic field changes within this volume, the rate of dephasing nuclear spins that contribute to the signal can be locally different. For example, when using a gradient echo sequence, this can result in different echo time points. The signal strength can be reduced. This can reduce MR visibility. For example, the material may further have a T2 ^* relaxation time of the nuclear spin in the volume, which relaxation time is a factor 2, preferably a factor 4 smaller than the corresponding T2 ^* relaxation time of the substrate material, ie 1/2 times. , Preferably 1/4 times smaller.

Here, the material means a material including a base material and a doping material. The T2 ^* relaxation time is known to those skilled in the art for magnetic field inhomogeneities and is related to the dephasing of the nuclear spin perpendicular to the static position (spin-spin relaxation). The T2 ^* relaxation time may mean, for example, the time after a one-time 90 ° HF pulse, after which the transverse magnetization is restored to 37% of its starting value. For example, in a gradient echo MR imaging sequence, T2 ^* time can be decisive for signal strength or signal-to-noise ratio, so-called T2 ^* weighted image formation.

  In this regard, the local change or visualization of eg magnetic susceptibility in MR imaging based on doped doping material can be characteristically dependent on the particle size and grain shape of the doping material. The particle size of the doping material may be less than 200 μm, preferably less than 10 μm. In particular, the particle size may be in the range of about 100 μm, for example. The term “particle size” means, for example, the average particle size. The doping material can have a distribution which can be described in particular by a Gaussian curve, for example, in terms of particle size. Corresponding scenarios are known to those skilled in the art. The small particle size can also have advantages with respect to further properties of the material, eg, robustness, conductivity, brittleness, etc.

In this regard, the doping material includes magnetic nanoparticles, and the particle size of the doping material can be less than about 1 μm, preferably less than about 100 nm. For example, ferromagnetic nanoparticles are known as magnetic nanoparticles. Typically, magnetic nanoparticles can have a particularly small particle size, for example a size in the range of 20-50 nm. In such a case, it may be possible to achieve a particularly uniform blending even in a volume clearly smaller than 1 mm ³ , for example a volume as large as 1 μm ³ .

Ferromagnetic nanoparticles can have a particularly high magnetic susceptibility and can thus cause particularly strong changes in the local magnetic field. In that way, the difference in the local dephasing of the nuclear spin can result in a particularly large and the visibility in MR imaging can be reduced particularly strongly. In other words, the use of ferromagnetic nanoparticles can result in a particularly short T2 ^* relaxation time for the substrate material.

  For example, the proportion can be in the range of 0.1% to 80%, preferably in the range of 1% to 20%, particularly preferably in the range of 9% to 11%. For example, this percentage can mean weight percent or volume percent.

  In particular, the ratio can be directly related to the macroscopic susceptibility of the material, ie, the susceptibility measured averaged over a large portion of the material. As such, a larger proportion of the doping material results in the material's macroscopic susceptibility taking a larger absolute value. Therefore, on the one hand, it may be desirable to add a large proportion of the doping material to the substrate material. On the other hand, it may be desirable to maintain certain material, for example electrical and mechanical material properties of the material, which may be exacerbated by the excessive proportion of doping material added. For example, it is desirable to obtain a particularly robust material, but it becomes brittle due to an excessive proportion of doping material.

  In this regard, the substrate material may be, for example, an acrylonitrile-butadiene-styrol (ABS) composite. Such synthetic materials are also known as telluran synthetic materials (Terluran, trade name of BASF). In a particularly preferred mode of implementation, the substrate material can be, for example, ABS GP22.

  In general, the substrate material can be selected from the group comprising the following elements: thermoplastics, thermoplastic elastomers, elastomers, thermosets, foamed plastics. Such materials have favorable properties with respect to strength, elasticity, heat resistance, slight electrical conductivity, magnetic properties and the like. As the substrate material, a lexan synthetic substance can also be used.

Accordingly, the doping material can be either diamagnetic (magnetism <0) or paramagnetic (magnetism> 0), for example. For example, the doping material can be selected from a first group of diamagnetic materials that include graphite, bismuth as components. However, the doping material can also be selected from a second group of paramagnetic materials comprising platinum, chromium, tungsten, ferritin as components. In particular, such a material having a relatively large value of magnetic susceptibility can be used, and as a result, the local deviation of the magnetic field from the value of the basic magnetic field in the magnetic resonance facility is particularly large. Correspondingly, the local dephasing of nuclear spins becomes significantly different, so that the value of T2 ^* relaxation time can be particularly slight. The doping material can be palladium or can include carbon nanotubes.

For example, the material can have a macroscopic susceptibility substantially equal to that of water or tissue or organic material or air. Macroscopic susceptibility can mean, for example, the value of susceptibility as measured in a special case of a large part of the material and thus on a macroscopic scale. For such parts, there is an averaged blend of substrate material and one or more doping materials with different magnetic properties (diamagnetic, paramagnetic, ferromagnetic). For example, the portion may have a scale that is equal to or greater than the volume. Values for the above mentioned susceptibility values are known to those skilled in the art, for example, χ = 9 × 10 ⁻⁶ for water or tissue, or χ = 6 × 10 ⁻⁶ for organic materials, Or for air, χ = 0.38 × 10 ⁻⁶ .

As detailed above, according to the point of view discussed therein of the present invention, the material can have the effect of locally changing the magnetic susceptibility based on fine mixing of the substrate material and the doping material. . Thereby, the T2 ^* relaxation time results in particularly little and the material can have reduced visibility in MR imaging. Furthermore, for the case where the material has a macroscopic averaged magnetic susceptibility having one of the above values, another effect of susceptibility matching is in addition to this reduced MR visualization effect. The effect approaches. That is, for example, a susceptibility gradient can appear at the air-tissue interface, i.e., a change in susceptibility can appear as a function of location. For example, the value of magnetic susceptibility changes from χ = 0.38 × 10 ⁻⁶ to χ = 9 × 10 ⁻⁶ on the skin surface. This can result in the local magnetic field value deviating from the value of the basic magnetic field of the MR equipment in and around this region. The MR imaging can then have so-called susceptibility artifacts in this region, such as deviations in the MR image.

  However, if the material has a correspondingly matched value, the material-tissue interface will be significantly affected if the material is used for an MR equipment component such as an HP coil or shim pad, for example, in the vicinity of the body. It can be achieved that no magnetic susceptibility gradient appears. In other words, the susceptibility mismatch can be shifted to a region that does not contribute to MR image formation. Thereby, the magnetic susceptibility artifact in the MR image can be reduced.

  However, it is also possible that the material has a magnetic susceptibility that deviates from these values described above for water or tissue or air or organic material. This can be advantageous, for example, in order to achieve particularly reduced MR visibility. In this way, material property optimization can be done in other words in terms of reducing MR visibility, which is primarily related to the microscopic location dependence of magnetic susceptibility, while macroscopic magnetization. The rate is not important.

  For example, in particular, the material may include another magnetic doping material mixed in different proportions, and there may be uniform mixing of the substrate material, the doping material, and another doping material in the volume. The sign of the susceptibility of the doping material may not be equal to the sign of the susceptibility of the doping material. Thus, for example, a doping material can be paramagnetic and another doping material can be diamagnetic (or vice versa). The doping material or another doping material can also be ferromagnetic.

In such a case, the microscopic susceptibility gradient has a particularly large value, or there are many different local magnetic field strengths in the MR imaging voxels, for example, in particular a slight T2 ^* relaxation time effect. Can be achieved. At the same time, it is possible to appropriately set the value of the macroscopic susceptibility of the material by appropriately selecting the proportion of the doping material and another proportion of the other doping material depending on the susceptibility of both the doping materials. Is possible.

ここでＶ_B、Ｖ_Dnは基体材料及びドーピング材料のそれぞれの体積割合である。それ故次式が成立する。

例えば、式１から、２つのドーピング材料、すなわちグラファイト粉末χ_D1＝−２０５×１０^-6及びパラジウム粉末χ_D2＝−８０６×１０^-6に対しそれぞれＶ_D1＝５．２０％及びＶ_D2＝０．２０％について非磁性χ_B＝０の基体材料に混ぜ合わされることで、χ_m＝−９×１０^-6の結果が得られる。これは人の組織の値に対応する。この場合基体材料は例えばＡＢＳ ＧＰ２２であってよい。 In general, N doping materials each having a magnetic susceptibility χ _n can be added to the base material (magnetic susceptibility χ _B ). As a result, the macroscopic magnetic susceptibility χ _m is as follows.

Here, V _B and V _Dn are volume ratios of the base material and the doping material, respectively. Therefore, the following equation holds.

For example, from Equation 1, V _D1 = 5.20% and V _D2 = 0 for two doping materials: graphite powder χ _D1 = −205 × 10 ⁻⁶ and palladium powder χ _D2 = −806 × 10 ⁻⁶ , respectively. When mixed with non-magnetic χ _B = 0 substrate material for .20%, a result of χ _m = −9 × 10 ⁻⁶ is obtained. This corresponds to the value of the human organization. In this case, the substrate material may be, for example, ABS GP22.

For example, it is also possible to mix this substrate material with V _D1 = 5% graphite and V _D2 = 0.50% or V _D2 = 1.00% palladium, from -6.6 ppm to -2 This results in a macroscopic susceptibility of .6 ppm.

  The above examples are purely illustrative. In general, the proportion of doping material may be different from that of another doping material, so that the macroscopic susceptibility is equal to a certain defined value. In particular, the macroscopic magnetic susceptibility of a material can be equal to the value of, for example, water, air, tissue or organic material by mixing a doping material and another doping material. In particular, the particle size of another doping material can be, for example, less than 200 μm, or preferably less than 10 μm. In general, the corresponding requirement for another doping material or the same requirement can be set, as described above for the doping material.

According to yet another aspect, the present invention relates to a method of manufacturing a material for use in a magnetic resonance facility, the method comprising melting a substrate material made of a synthetic material with an extruder and in a volume of less than 1 mm ³ . Including mixing a proportion of the magnetic doping material such that there is uniform mixing. Such a method can be used to obtain materials for use in magnetic resonance equipment according to another aspect of the present invention.

  According to another aspect, the present invention relates to a magnetic resonance facility having a sensitivity region, wherein the magnetic resonance facility is configured to detect magnetic resonance data for image formation within the sensitivity region. Includes components in the sensitivity region for image formation. The magnetic resonance facility is characterized in that the components include materials for use in a magnetic resonance facility in accordance with the aspects of the invention discussed above. For example, the component may relate to a high frequency coil and may involve a table or bed or shim pad for bringing a patient into the MR facility. When materials in accordance with the present invention are used to manufacture such components, these components can have reduced visibility in MR imaging. These components can also advantageously have a magnetic susceptibility that matches the surrounding magnetic susceptibility so that susceptibility artifacts in MR imaging can be reduced.

  Naturally, the features of the embodiments described at the outset and the aspects of the invention can be combined with each other. In particular, the features can be used not only in the described combinations, but also in other combinations or independently selected without departing from the field of the invention.

  The above-mentioned characteristics, features and advantages of the invention and the manner in which they are achieved will become clearer and more apparent in connection with the following description of the embodiments described in detail in connection with the drawings.

It is a figure which shows the material which has a base material and the doping material mixed. It is a figure which shows the particle size distribution of doping material. It is a figure which shows the magnetic field change on the 1st representative length scale based on the mismatch of a magnetic susceptibility. It is a figure which shows the magnetic field change on the 2nd representative length scale based on a microscopic magnetic susceptibility gradient, The 2nd representative length scale is smaller than the representative length scale of FIG. FIG. 6 shows a material having a doping material mixed with a base material and another doping material. It is a figure which shows the component of MR equipment.

  BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail below on the basis of advantageous embodiments with reference to the drawings. In the figures, the same reference numerals represent the same or similar elements.

  FIG. 1 represents a material 1 composed of a base material 2 and a doping material 3 mixed. The doping material is shown embedded in the substrate material 2 in the form of grains or clusters (aggregates). A particle size of 20 is displayed.

  In FIG. 2, the particle size distribution 21, ie the frequency of different particle sizes, is shown by way of example. The maximum value of the particle size distribution 21 can indicate the particle size 20, for example. In FIG. 2, the particle size distribution 21 is drawn by a Gaussian curve. For example, the particle size 20 may be less than 200 μm, preferably less than 100 μm, particularly preferably less than 10 μm.

Referring again to FIG. 1, it is clear that there is a concentration shift from the macroscopic mean value of the doping material or substrate material. This is due to the grains or clusters of the doping material 3. Uniform blending, and therefore blending that matches the macroscopic value of a large volume at extreme substrate and doping material concentrations, is achieved for a volume 10 having a size of 1 mm ³ . In other words, the concentration of the materials 2 and 3 involved varies microscopically with a representative length of about 1 mm. When averaged over a greater length, the value is equal to the macroscopic average value.

Such parameters are related to the manufacturing process, for example. As such, the preparation of the doping material can result in smaller particle sizes and so uniform and fine mixing. For example, the substrate material 2 may be a synthetic material, such as ABS GP22. For example, the use of a twin screw extruder to melt the synthetic material can allow a particularly fine and uniform mixing.

  The doping material 3 is a magnetic material, i.e. has a magnetic susceptibility not equal to zero. The doping material 3 may be ferromagnetic, diamagnetic or paramagnetic, for example. In particular, the doping material 3 can have a magnetic susceptibility different from that of the substrate material 2. As a result, a change in magnetic susceptibility, that is, a local variation in magnetic susceptibility appears on the above-described representative length scale, that is, in the volume 10. This means that different magnetic susceptibility values exist in the volume 10 depending on the position (location). For example, the doping material 3 can be graphite or carbon nanotubes or bismuth or palladium or platinum or chromium or tungsten or ferritin. The doping material can be mixed, for example, in a proportion of 5 to 15% by weight to volume%.

For example, material 1 can be used for construction requirements in MR equipment. There is typically a basic magnetic field to polarize nuclear spins. Based on locally different magnetic susceptibility in volume 10, the basic magnetic field is different in volume 10. Therefore, nuclear spins at different locations within the volume 10 dephasing at different speeds. When the MR facility is integrated over volume 10 for MR imaging, material 1 will have reduced visibility since the T2 ^* relaxation time is reduced. In particular, this may correspond to a so-called gradient echo MR imaging sequence, which is known to those skilled in the art. The integration for MR imaging for the volume 10 (so-called voxels) can be caused, for example, by the limited spatial resolution of the MR equipment, or the correspondingly accumulated measurements can be used to increase the signal-to-noise ratio. This may be necessary based on the limited sensitivity required to detect.

In the case of a relatively low homogeneity blending of material 1, for example in the blending of materials on a representative length scale that is greater than the spatial resolution of the MR equipment, there is a relatively slightly reduced T2 ^* relaxation time. It should be understood that this is possible. In that way, there can be a relatively slight change in magnetic field strength within the volume 10, so there is no different dephasing condition for nuclear spins.

  Various mentioned representative length scales are shown in FIGS. In FIG. 3, the value of the magnetic field 30 (broken line, left scale) is shown as a function of position 32 for a sudden jump in local susceptibility 31 (solid line, right scale). As is clear from FIG. 3, the value of the magnetic field 30 in the region around the susceptibility jump deviates from a constant value (for example, the value of the basic magnetic field in the MR equipment). For example, when jumping from air to human tissue, it can therefore appear on the skin surface.

  The typical length scale of FIG. 3, ie the length scale over which the value of the magnetic field 30 varies, is centimeters, about 5-10 cm. However, the spatial resolution of voxels or typical MR equipment is very small. In a typical MR facility, a spatial resolution of 1 mm is achieved. The corresponding side length of volume 10 is shown as length I-I '. However, on such a length scale, the magnetic field 30 does not change or only changes slightly in the scene of FIG. Therefore, there will be a substantially uniform magnetic field within the voxel and either reduced MR visibility will not be achieved, or only slightly reduced visibility will be achieved.

Correspondingly, in FIG. 4, the value of the magnetic field 30 is shown on the upper side as a function of the location 32 with respect to the magnetic susceptibility 31, and the magnetic susceptibility varies on a very short length scale. The same length II ′ is shown in FIGS. 3 and 4, respectively. Such a change in magnetic susceptibility as a function of position 32 is, for example, when the mixing of the substrate material and the doping material 2, 3 in the volume 10 of less than 1 mm ³ is uniform for the material 1 according to the aspect of the invention, Thus, it is achieved particularly when fine mixing is present. For example, the length II ′ can represent a length of 1 mm. Figure 4 As is apparent from, the magnetic field 30 can take different values in voxel MR imaging, the resulting material 1 T2 ^* relaxation time, for example, Factor to T2 ^* relaxation time of the substrate material 2 2 Or it is shortened by 4, that is, it is shortened to 1/2 times or 1/4 times.

On the lower side of FIG. 4, the direction 30a of the magnetic field is shown. Since the magnetization of the grains of the doping material 3 (see FIG. 1) can be oriented substantially differently, the direction 30a of the magnetic field on the representative length scale can also change. This can also have an impact on the T2 ^* relaxation time.

  FIG. 5 shows a material 1 that contains a further doping material 4 in addition to the doping material 3. This further doping material 4 may also be magnetic. In particular, the further doping material 4 can have a magnetic susceptibility with a different sign relative to the magnetic susceptibility of the doping material 3. In other words, for example, the doping material 3 may be paramagnetic or ferromagnetic (diamagnetic), while the other doping material 4 may be diamagnetic (paramagnetic or ferromagnetic).

The use of material 1 can provide two effects. That is, first of all, the location dependence of the magnetic susceptibility in the volume 10 can be particularly strong. Thereby, the local magnetic field can be changed particularly strongly, so that the T2 ^* relaxation time of the nuclear spin can be reduced particularly strongly. Material 1 may thus have reduced visibility in MR imaging. Second, by appropriately selecting the proportions of the doping materials 3, 4 based on their magnetic susceptibility, the macroscopic magnetic susceptibility of the material 1 is equal to a predetermined value, for example air, water, tissue or organic Equal to the material is achieved. This is illustrated by equations 1 and 2 above. This may make it possible to reduce susceptibility artifacts in MR imaging. Magnetic susceptibility artifacts can be caused by local shifts in magnetic field strength 30, as illustrated in FIG. However, it should be understood that the critical length scale for both of these effects has a different order, as described above with respect to FIGS.

  FIG. 6 schematically illustrates components 41, 42, 43, which can be made partially or primarily from material 1. Shown is a table or bed 41 on which a patient can be placed and carried into the MR facility. In addition, an HF local coil 42 is shown that can be used to detect MR signals or to excite magnetization by irradiation with HF pulses. A shim pad 43 is also recognized. The shim pad 43 has a specific magnetic susceptibility, approximately that of human tissue. When the shim pad is placed in the vicinity of the human body during MR imaging, a susceptibility jump appears at a location that is not part of the MR imaging (eg, at the air-shim pad interface) as illustrated in FIG. Thereby, for example, susceptibility artifacts near the skin can be reduced.

  Therefore, a reduction in the MR visibility of material 1 is achieved by doping the MR imaging substrate material with doping materials 3 and 4 that are magnetic or weakly magnetic, eg, fabricated as micro- or nanoparticles. . This in particular makes it possible to use all customary materials, for example conventional synthetic materials, also in the imaging volume of MR equipment. This saves costs, realizes new mechanical functions such as flexible coils, coils with synthetic joints, lighter patient tables, etc. and improves patient comfort. As the base material 2, thermoplastic materials, thermoplastic elastomers, elastomers, thermosetting materials, and polystyrene foam are particularly suitable. As the doping material 3, diamagnetic materials, particularly strong diamagnetic raw materials such as graphite and bismuth, and a wide variety of paramagnetic raw materials are suitable. The doping material 3 or another doping material 4 can be added in the range of 1 to 80% by weight, preferably in the range of 5 to 15% by weight, particularly preferably in the range of 9 to 11% by weight. The particle size is, for example, 100 μm, preferably smaller than 10 μm. In particular, in the case of nanoparticles having a particle size smaller than 100 nm, a ferromagnetic raw material can be used.

  In the preparation of the mixture of the base material 2 and the doping materials 3, 4, it is advantageous to use a twin screw extruder, since a particularly fine and uniform distribution is achieved by the mixing of the materials 2, 3, 4.

  Although the invention has been illustrated and described in detail by way of advantageous embodiments, the invention is not limited by the disclosed examples, and other variations therefrom will depart from the protection scope of the invention by those skilled in the art. Can be derived without

DESCRIPTION OF SYMBOLS 1 Material 2 Base material 3 Doping material 4 Another doping material 10 Volume 20 Particle size 21 Particle size distribution 30 Magnetic field 30a Magnetic field direction 31 Magnetic susceptibility 32 Position 41 Component (table or bed)
42 Components (high frequency local coil)
43 Components (Shimpad)

Claims (15)

Includes a substrate material (2), a defined percentage by admixed by magnetic doping material (3) and another magnetic doping material which is admixed with a different rate (4),
Within a volume (10) of less than 1 mm ³ there is a homogeneous mixing of the substrate material (2) , the doping material (3) and the further doping material (4) ;
A material for use in a magnetic resonance system, wherein the sign of the magnetic susceptibility of said another doping material (4) is not equal to the sign of the magnetic susceptibility of said doping material (3) .   2. Material according to claim 1, wherein the particle size (20) of the doping material (3) is smaller than 200 [mu] m.   The material according to claim 1 or 2, wherein the doping material (3) comprises magnetic nanoparticles and the particle size (20) of the doping material (3) is smaller than 1 µm.   The material of claim 3, wherein the magnetic nanoparticles are ferromagnetic.   The material according to any one of claims 1 to 4, wherein a proportion of the doping material is in a range of 0.1% to 80%.   The material according to any one of claims 1 to 5, wherein the substrate material (2) is an acrylonitrile-butadiene-styrol (ABS) synthetic material.   The material according to any one of claims 1 to 6, wherein the substrate material (2) is selected from the group of thermoplastic substances, thermoplastic elastomers, elastomers, thermosetting substances, foamed plastics.   Said doping material (3) is selected from a first group of diamagnetic materials comprising graphite, bismuth as components, or from a second group of paramagnetic materials comprising platinum, chromium, tungsten, ferritin as components. The material according to any one of claims 1 to 7, which is selected.   The material according to any one of claims 1 to 8, wherein the material (1) has a macroscopic magnetic susceptibility equal to that of water, tissue, organic material or air.   9. A material according to any one of the preceding claims, wherein the material (1) has a macroscopic magnetic susceptibility that is not equal to at least one magnetic susceptibility of water, tissue, organic material and air. The material (1 ) in the volume (10) has a T2 ^* relaxation time of nuclear spin, the relaxation time being ½ or less of the corresponding T2 ^* relaxation time of the substrate material (2). Item 11. The material according to any one of Items 1 to 10. 11. A material according to any one of the preceding claims, wherein the particle size of the further doping material (4) is smaller than 100 [mu] m. To produce a material (1) for use in a magnetic resonance system,
The base material (2) made of a synthetic substance is melted by an extruder,
The base material , the magnetic doping material (3) and another magnetic doping material in which the sign of magnetic susceptibility is not equal to that of the base material , the magnetic doping material (3) , so that there is uniform mixing within a volume (10) of less than 1 mm ³ (4) The manufacturing method of the material for using for a magnetic resonance system which mixes. The method of claim 13 used to manufacture the material (1) according to any one of claims 1 to 12. Detect magnetic resonance data for image formation within the sensitivity region,
Containing components (41, 42, 43) in the sensitivity region for the image formation,
Magnetic resonance system including a material (1) according to any one of said component (41, 42, 43) is according to claim 1-12.

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